Recent years, development of SOC (System on a chip) structured so that it might have various functions by mounting analog/digital circuits whose operating frequency is a gigahertz (GHz) region on 1 chip is performed briskly.
In such SOC, incorporating an electronic device for measures against the noise in the circuits for stabilization of circuit operation is performed.
For example, the structure which has arranged a bypass condenser (decoupling capacitor) which has an MOS structure between a power supply wiring and a ground wiring for control of the power source noise of an external power source is shown in Patent Reference 1.
The structure which has arranged a decoupling capacitor having an MOS structure between a power supply wiring and a ground wiring is shown also in Patent Reference 2.
A decoupling capacitor is used in order to suppress rapid fluctuation of power supply voltage or to prevent local lowering of power supply voltage, and the larger the capacity is, the higher its effect of stabilizing power supply voltage is. Therefore, it is said that it is desirable to incorporate as many decoupling capacitors as possible.
[Patent Reference 1] Japanese Unexamined Patent Publication No. 2002-246548 (FIG. 4, FIG. 6)
[Patent Reference 2] Japanese Unexamined Patent Publication No. 2002-76271 (FIG. 2)